IN THE NEWS

Using technology to track buses is just one way to help transit agencies do better and inform riders

On Service Reliability...

Recently, the Transit Riders' Alliance asked its e-mail list what transit improvements people would like to see. One of the most common responses we received mentioned the elimination of bus bunching, and more frequent and reliable service.

We'd like to take a moment to address those concerns, and let you in on what transit agencies are doing to make service more reliable today.

Bus Bunching

"Bus Bunching" is one of those things that happens on transit systems all around the world, and it is probably the thing we most often hear people wanting to see fixed. From the perspective of a rider, you experience this: You wait longer than normal for a bus, and then two or three come all at the same time.

As transit riders, we've experienced it ourselves.

How does it happen?

Consider this scenario:

A bus leaves its terminal on time, and stays on-schedule for a mile or two. However, an illegally parked car causes a traffic backup that delays the bus by about four minutes. With buses on this route scheduled at 12-minute intervals, the next bus after it is already only eight minutes behind--the following bus is catching up slightly. It's also now been 16 minutes since a bus reached the stops ahead.

Now, with a 33% longer wait between buses, there are potentially 33% more passengers waiting for the bus--all because of a delay of just a few minutes. It stops at more stops and each stop takes longer, delaying it further. The delay begins to snowball.

With a shorter headway between the delayed bus and its follower, and less people on it, the follower is easily able to maintain schedule, and by the time its leader is delayed a full 12 minutes, you've got a "bunch." With each having to stop at every or every other stop, they leapfrog each other and are stuck in a bunch.

A simple delay of just a few minutes can really have an impact. It doesn't always have to be a singular delay, though.

Delays add up

Often, minor delays can add up. Here are just a few causes of delays that, when added up, can lead to bunching:

Illegally parked cars or trucks (double-parked, sitting in designated bus stops, parked in rush-hour "no parking" zones)
Unusually heavy traffic for a given time of day
An equipment problem or failure on a bus
A street blockage, road work, or detour
Deliveries that result in double-parked trucks

It's also notable that the longer a route is, the more opportunities there are for these small delays to add up. This is why long routes with high frequency are often prone to the phenomenon. But, generally, bunching is the result of delays.

What can be done to prevent delays?

Transit agencies are aware of these problems and take a number of measures to prevent or alleviate bunching. Often, these measures are focused on simply maintaining regular headways during more frequent service, which is generally more important to riders than precision when buses are running every few minutes.

Here are some measures transit agencies take to deal with delays:

Working with local traffic enforcement to ensure drivers obey restrictions such as no stopping or standing in bus stops or bus-only lanes
Writing schedules with extra time to anticipate the likelihood of regular delays
Tracking schedule adherence and modifying schedules to be more practical or realistic
Longer turnaround times so bus operators, even when arriving late, can still leave on time for their next trip
Traffic signal or lane priority for transit vehicles
Using real-time information so transportation managers can anticipate and resolve problems on-the-fly

Sometimes delays are unavoidable. Inclement weather, accidents, and equipment problems can occur without warning, and traffic can be very unpredictable in cities. In fact, the Chicago area has some of the most unpredictable (if not the most unpredictable) traffic patterns in the country[1], and it presents some real challenges for the region's providers of bus service: CTA and Pace.

Adding time to schedules so operators have more wiggle room helps, but add too much and buses have to go slow to keep from getting ahead, which can create gaps in service and delay buses behind it as they have unusually-large passenger loads.

In some cases, resolving the kinds of delays that cause bunching are simple (but drastic), such as having one bus skip stops or run "express" for a stretch, or even have a bus "short-turned" at a certain point and head back the other way, without going all the way to the end of the line.

Unfortunately, some of these more drastic responses can cause further inconvenience for riders, which is why transit agencies avoid using them and instead focus on preventing bunches in the first place.

As the old saying goes: an ounce of prevention is worth a pound of cure.

New technology helps buses and trains

There are several areas where technology can help with the problem of bus bunching and help rail lines stay on-time, and can keep riders informed.

For years now, many transit agencies (including in Chicago) have been using GPS data collected on buses to track how well buses progress on their routes, how well they can adhere to written schedules, and even where people are boarding and exiting buses. This kind of information helps in identifying problem areas, and also in writing schedules that can be better adhered to. The result is more regular and reliable service.

Today, many agencies are installing cellular modems or other devices to transmit real-time data back to transit agencies for each bus. This allows supervisors to see a larger picture than they could in the past, and catch mounting delays much earlier. This data can also be used to benefit riders by providing precise times for when a bus will arrive, and empowers people to make smarter decisions and get the most out of transit (especially when people have multiple options).

Similarly, on rail transit, new switching, signal, and train communication improve reliability and safety. In New York, some subway lines are being converted to being computer-controlled, so more trains can be run on a line safely and quickly. Passenger information systems on many railways help inform riders about delays that can affect their commute.

This kind of technology requires investment, and, fortunately for Chicagoans, is being made a priority. It's an example of how capital investments can improve the everyday experience--not just by upgrading facilities, but by implementing technology that can make supervisors and planners far more effective in making transit work right.

All transit systems can benefit from technology that helps supervisors better manage service and which informs riders--it's a smart investment.

A Working Fleet

Beyond just trying to mitigate the kinds of delays that affect service, an aging fleet of transit vehicles means less-reliable service and a more expensive service to provide.

When buses or trains are slow, break down, have equipment malfunctions that have to be dealt with en-route, or are otherwise outdated and inefficient, it costs more money to operate service and worsens delays. You need more buses and operators because they move more slowly, you spend time and money on repairs, and overall efficiency plummets.

Transit agencies having modern, reliable fleets, and ones that have the muscle to move the millions of people who use transit every day across Illinois quickly and reliably, is crucial for transit to work. Good buses and trains make transit reliable, accessible, and efficient, and the money saved can be applied elsewhere, to provide more and better service with less expense.

With transit agencies across Illinois with buses and train cars dating as far back as 40 years, it's not uncommon for problems to occur--and it's one more reason why continual capital investments are so important.

Footnotes

Schrank D. and Lomax T., Texas Transportation Institute. 2007. 2007 Annual Urban Mobility Report. Exhibit 12: You Should Plan for Much Longer Travel Times. p.13 ( PDF)